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Solve the system of equations:
[tex]\[ \left\{
\begin{array}{l}
3x - y + z = 7 \\
2x + y - 2z = 5 \\
4x + 7y + 5z = 1
\end{array}
\right. \][/tex]

Sagot :

To solve the given system of linear equations:

[tex]\[ \begin{cases} 3x - y + z = 7 \\ 2x + y - 2z = 5 \\ 4x + 7y + 5z = 1 \end{cases} \][/tex]

we need to find the values of [tex]\( x \)[/tex], [tex]\( y \)[/tex], and [tex]\( z \)[/tex] that satisfy all three equations simultaneously.

### Step 1: Write the equations in matrix form

We can represent the system of equations as a matrix equation [tex]\( A \mathbf{x} = \mathbf{b} \)[/tex] where

[tex]\[ A = \begin{pmatrix} 3 & -1 & 1 \\ 2 & 1 & -2 \\ 4 & 7 & 5 \end{pmatrix}, \quad \mathbf{x} = \begin{pmatrix} x \\ y \\ z \end{pmatrix}, \quad \mathbf{b} = \begin{pmatrix} 7 \\ 5 \\ 1 \end{pmatrix} \][/tex]

### Step 2: Use an appropriate method to solve the linear system

Without carrying out the detailed calculations here, we apply methods such as substitution, elimination, or matrix operations (like Gaussian elimination or using the inverse of matrix [tex]\( A \)[/tex]) to solve the system.

### Step 3: Find the solution

The result from solving this system is:

[tex]\[ x = \frac{194}{85}, \quad y = -\frac{63}{85}, \quad z = -\frac{10}{17} \][/tex]

### Step 4: Interpret the solution

Therefore, the values of [tex]\( x \)[/tex], [tex]\( y \)[/tex], and [tex]\( z \)[/tex] that satisfy all three equations are:

[tex]\[ x = \frac{194}{85}, \quad y = -\frac{63}{85}, \quad z = -\frac{10}{17} \][/tex]

These result in the exact solution to the given system of linear equations.